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Tuesday, September 16, 2014

Weekly Propagation Forecast Bulletins

Product: Weekly Highlights and Forecasts

:Issued: 2014 Sep 15 0717 UTC
# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center
# Product description and SWPC web contact www.swpc.noaa.gov/weekly.html
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# Weekly Highlights and Forecasts
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Highlights of Solar and Geomagnetic Activity 08 - 14 September 2014
Solar activity ranged from low to high levels during the period. Moderate levels were reached on 8, 11, and 14 September with high levels reached on 10 September. Moderate levels were first reached on 09 September at 0029 UTC when active sunspot region 2158 (N16, L=087, class/area Dkc/440 on 11 September) produced a long duration M4/1n flare. This flare had associated Type II (999 km/s estimated shock velocity) and Type IV radio sweeps, a 10cm (370 sfu) radio burst, and an symmetrical, full-halo coronal mass ejection (CME) which was first observed in LASCO/C2 imagery at 09/0006 UTC. The majority of the ejecta appeared to be heading north and east of the Sun/Earth line, however, it was later determined this event contained an Earth-directed component. On 10 September, conditions reached High levels as Region 2158 produced a X1/2b flare at 1745 UTC. It also had associated Type II (3750 km/s estimated shock velocity) and Type IV radio sweeps, a 10cm (1300 sfu ) radio burst, and an Earth-directed full halo CME. On 11 September, Region 2166 (N13, L=352, class/area Dao/60 on 14 September) produced an M2 flare at 1526 and an M1 flare at 2126 UTC, just prior to rotating on to the visible disk. After returning to low levels on 12 and 13 September, conditions again rose to Moderate levels as Region 2157 (S14, L=98, class/area Ekc/540 on 6 September) produced an M1/2n flare at 14/0216 UTC. The coronal mass ejection (CME) associated with this M-flare was observed off the west limb in SOHO/LASCO C2 coronagraph imagery beginning at 14/0248 UTC, but was deemed to be well off the Sun-Earth line. Other activity included a filament eruption observed in SDO/AIA 193 imagery beginning at 12/1749 UTC west of Region 2158 near center-disk. SOHO/LASCO C2 imagery showed a coronal mass ejection (CME) beginning at 12/1936 UTC that was mostly obscured by a larger backsided CME off the NNE limb that preceded it beginning at 12/1836 UTC. WSA-ENLIL modeling of the event indicates a likely CME arrival around midday on 16 September.
The greater than 10 MeV proton flux was elevated on 8 and 9 September due to a particle enhancement from an event the week prior. Late on 10 September, levels began a quick rise following the X1/2b flare from Region 2158, mentioned earlier. By 11 September, the greater than 10 MeV levels had reached a peak of 28 pfu (S1 - Minor), but then leveled off for the next 24 hours. Storm levels briefly reached the S2 (Moderate) threshold, in conjunction with the arrival of the CME, and reached a maximum of 126 pfu at 12/1355 UTC. During this time, the greater than 100 MeV proton flux levels began to rise as well, reaching the 1.2 pfu at 11/0425 UTC level before tapering off shortly thereafter.
The greater than 2 MeV electron flux at geosynchronous orbit was at normal levels on 8, 9, 11, 13, and 14 September, and reached moderate levels on 10 and 12 September.
Geomagnetic field activity was at quiet to severe storm levels during the period. Quiet to unsettled levels occurred from 8 to 11 September, with an isolated active period on 11 September. A geomagnetic Sudden Impulse (33 nT) was observed at the Boulder magnetometer at 11/2346 UTC, indicating the arrival of the 09 September CME as anticipated. The geomagnetic field responded, pushing geomagnetic field conditions to minor storm levels. Conditions moderated for approximately 9 hours back at quiet to unsettled levels, until the second CME arrived at Earth. Total field rose to a max of 31 nT and solar wind increased to near 790 km/s by late on 12 September. A geomagnetic sudden impulse of 43 nT was observed at the Boulder magnetometer at 12/1555 UTC. Conditions then increased to minor to severe storm levels for the next 9 hours. Conditions fell to active levels early on 13 September and continued to decline to quiet levels by mid day as the Bz component remained in a northward orientation (not well connected). Quiet conditions remained through 14 September.
Forecast of Solar and Geomagnetic Activity 15 September - 11 October 2014
Solar activity is expected to be low with a chance for M-class flares through 27 September due to returning Regions 2149 (N09, L=284) and 2151 (S08, L=253). Activity is then likely to be moderate (R1-R2/Minor-Moderate) with a chance for X-class flaring (R3-Strong or greater) through the remainder of the period due to Regions 2157 and 2158 returning to the visible disk.
There is a chance for a greater than 10 MeV proton event from 29 September through the end of the period due to potential significant flare activity from Regions 2157 and 2158.
The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at normal to moderate levels from 15 to 18 September, before returning to normal levels through 25 September. Conditions should increase to normal to moderate with a chance for high levels from 26 September through 1 October in response to the recurrent coronal hole high speed stream (CH HSS). Conditions should fall back to normal to moderate levels from 2 - 11 October, with a chance for high levels from 7 to 9 October due to another CH HSS.
Geomagnetic field activity is expected to be at mostly quiet levels from 15 to 24 September, with isolated unsettled levels on 16 and 17 September, due to a recurrent CH HSS combined with CME activity from 12 September. Another recurrent CH HSS is expected to return on 25 September, making unsettled to active conditions likely through 30 September. Mostly quiet conditions are expected from 1 October to 5 October. A weak positive polarity coronal hole feature is likely to bring conditions up slightly, to the quiet to unsettled levels on 6 - 7 October, before returning to mostly quiet conditions for the remainder of the period.